In the past, many electric string instruments have been devised, among these are string instruments which have employed substantially rigid body construction. However, while solving problems of durability and loudspeaker feedback, such string musical instruments have not provided the dynamic playing response or tonal qualities expected from fine acoustic instruments. This is due in part to the lack of acoustical interaction between the strings, body, and neck structures of such rigid instruments. In these rigidly constructed string instruments, the energy imparted to the strings during performance is confined substantially to the strings and is unable to extend beyond the capacity of the string's maximum excursion. Thus, the dynamic range of such rigidly constructed instruments is limited, particularly in response to vigorous playing. Further, such rigid structures tend to store rather than dissipate higher frequency acoustical energy and thus display undesirable reverberation and resonances at audible frequencies. U.S. Pat. No. 3,769,871 to Joel Cawthorne, U.S. Pat. No. 4,192,213 to Ned Steinberger and U.S. Pat. No. 4,632,002 to Martin Clevinger, the inventor herein, are examples of these rigid body instruments.
In the present invention, accurate emulation of traditional string musical instrument behavior is achieved by assuring that elastic energy storage and damping characteristics provided by the present invention closely parallel those of the finest traditional acoustic string instruments wherein the bridge, soundboard, body and neck are increasingly set into vibrational excitation as the dynamic level of the string vibration is increased during performance. However, the present invention achieves the acoustical parameters through use of a novel tone engendering structure.
Many electric string musical instruments of the past have employed magnetic sound pickup devices. Most of these prior art systems generate electrical signals resulting from changes in the reluctance path of a magnetic field. Usually the strings are within the reluctance pathway, therefore movement of the strings causes changes in the reluctance path. These changes cause the intensity of the magnetic field to vary. These variations are sensed by magnetic field sensing means which produce electrical currents proportional to the variations. Usually a coil is used to produce electrical current in response to changes in magnetic field intensity.
The playing response and sonic quality produced by such variable reluctance pickups bear little resemblance to the playing response and sonic quality of acoustical instruments. The dynamic range provided by these pickups is insufficient to enable the player to achieve the full range of musical expression as is expected from quality acoustic instruments.
Many variations of magnetic pickup systems have been attempted. Some have mechanically coupled magnets or coils mechanically coupled to string bridge devices to simulate the timbre of acoustical instruments. Due to shortcomings in their mechanical structures and known problems including various inductive effects and noise inherent in these systems, sonic and performance qualities resembling those of acoustical musical instruments were never fully realized by these variable reluctance pickup systems.
Other string musical instruments, which in the past have used piezo electric materials in close mechanical coupling with vibrating strings, have not convincingly emulated the sound quality of acoustic instruments. Such instruments have generally employed string saddles or bridges under the pressure of the strings and bearing upon piezo electric materials. An example of this can be found in U.S. Pat. No. 4,491,501, to Lester M. Barcus. These saddles or bridges closely coupled the strings to piezo materials and produced signals analogous to changes in pressure upon the piezo elements. The output signal produced by these pressure changes was substantially devoid of acoustic effects which occur in elastic vibratile structures such as the bridge, soundboard, body and neck in traditional acoustic instruments. Typically audio signals produced by each independent string were mixed electrically. This resulted in a composite electrical signal mixdown of each string's isolated acoustic information, wherein the acoustical communication among strings through a common elastic structure, such as occurs in acoustic string instruments, was noticeably absent.
Unnatural over-emphasis of low amplitude sounds produced by bow friction or finger and plectrum impacts upon the strings were typical of closely coupled piezo systems. Further, the dynamic range of these closely coupled piezo systems was limited as the signal produced was confined to pressure changes caused solely by the vibration of the strings.
Attempts to enable vibrating strings to interact with certain vibratile structures mounted upon various solid or non-acoustic bodies are known. U.S. Pat. No. 4,635,523 to William Merchant used a traditional bass violin bridge bearing upon a plurality of elongated bridge supports. This required that the bridge rest upon at least two discrete supports which by their separate nature did not provide acoustical energy communication through a common soundboard in a fashion similar to traditional string instruments. While the location and placement of transducer means was not specified in this prior art string musical instrument, it is apparent that various add-on sound pickup attachments of the type used for amplification of traditional acoustic instruments would be required for electrical amplification, resulting in exposed wiring and vulnerability to damage. Further, the large size and the simple orthogonal shape of the elongate bridge supports introduced unrealistic resonances in the amplified signal. A traditional bridge structure of the type intended for excitation of a conventional acoustic body was used. Experiments have shown that in construction of an electric string musical instrument, a smaller bridge structure is more suitable for transmission of string vibration to electrical sensors. The large traditional bridge stored excessive amounts of acoustic energy which results in unwanted ringing and sonic coloration.
U.S. Pat. No. 4,632,002 to Martin Clevinger employed a compliant hanger structure with a substantially rigid crown in contact with the strings. This device suffered from undesirable resonances due in part to homogeneity and high mass density of the material required for its construction. Further, symmetrical geometry of the hanger structure caused standing waves at specific frequencies and reverberations resulting in undesirable resonant peaks. Since this prior art device substantially restricted acoustical energy to the strings and bridge/hanger structure, the output signal lacked the warmth and complexity expected from acoustic instruments.
Other prior art string instruments have used various bridge structures mounted upon or incorporating resilient materials such as rubber for enabling vibrating strings to produce low frequency displacements of these bridge structures. Among such inventions are U.S. Pat. No. 3,539,700 to Johnson and U.S. Pat. No. 3,113,990 to Zanessi. However, when rubber or similar elastic means were used, disproportionate acoustic energy losses with excessive damping of the strings occurred. An unnatural sound suffering from excessive low frequency transients is typical of such devices.
Other structures such as U.S. Pat. No. 4,607,559 to Richard Armin teaches a traditional violin bridge under tensioned strings bearing upon a carved soundboard acoustically suspended on a sealed cavity to provide sonic qualities similar to acoustic instruments. However, such prior art string instruments which employed hollow acoustic bodies suffered from excessive acoustical loudspeaker feedback as their thin plate construction became undesirably microphonic when the audio output signal was amplified at high levels. Further, these costly instruments were physically delicate and unstable in changing weather conditions. The present invention overcomes the objectionable characteristics and shortcomings of the foregoing while providing a greatly improved electric string instrument. More particularly, the present invention furnishes in an easily transportable durable and economical structure, highly desirable playing qualities similar to those possessed by delicate traditional acoustic instruments which have proved difficult to interface with modern audio equipment as found in broadcast, public address, and recording studio facilities. The present invention is readily adaptable to all modern musical facilities and situations.
The present invention may be applied to all string musical instruments and the benefits of the present invention may be well appreciated in string instruments which are frequently plucked as well as bowed. One example of such an instrument is the string bass. Fine timbre and even playing response at all levels of loudness have previously been available only in the finest traditional bass violins. The present invention achieves the desirable playing attributes of fine traditional bass violins with economy, improved durability, and with the added benefit of ready adaptability to recording, broadcast and public address applications, thus a string bass shall be described herein as an illustrative example of the present invention.